The present invention relates to an opto-semiconductor device and a method of fabricating the same, and particularly to improvements in the interconnection for its light-emitting part.
As an example of conventional opto-semiconductor device, an LED (light-emitting diode) array shown in Oki Kenkyu Kaihatsu (Oki Technical Review) 52[1], pp. 31 to 32 is illustrated in FIG. 1A and FIG. 1B. The illustrated LED array is formed of an N-type GaAs substrate 1 (hereinafter referred to as a substrate) on which an N-type GaAsP (e.g., GaAs.sub.0.6 P.sub.0.4 layer 2 is grown by VPE (vapor phase epitaxy), and then an insulating film such as Al.sub.2 O.sub.3 film 3 is formed, and a window 4 of 70 .mu.m.times.110 .mu.m is opened, and Zn is diffused through this window 4 to form a P-type GaAsP (e.g., GaAs.sub.0.6 P.sub.0.4) layer 5 in the N-type GaAsP layer 2. Then, an SiO.sub.2 film 6 is formed, as the second insulating film, over the entire surface to cover the window 4. An electrode contact window 7 (50 .mu.m.times.15 .mu.m) is then formed through the SiO.sub.2 film 6 at one end in its longitudinal direction of said P-type GaAsP 5 (light-emitting part). An Al electrode 8 is then formed so that it is connected to the P-type GaAsP layer 5 at the part of the window 7. The reason why the contact for the Al electrode 8 with the P-type GaAsP layer 5 must be situated at an end of the P-type GaAsP 5 is that Al does not permit passage of light, so to minimize the obstruction to the passage of light, the contact should be situated at an end. After forming a PSG (phospho-silicate glass) film 9 as a passivation film over the entire surface, the PSG film 9 at the part for the wire bonding of the Al electrode 8 is removed. An AuGeNi electrode 10 is vapor-deposited, as a negative electrode, on the rear (obverse) surface of the substrate 1.
FIG. 2 shows a second example of conventional opto-semiconductor device. The fundamental structure of this second device is identical to the first example shown in FIG. 1. But the connection of the Al electrode 8 with the P-type GaAsP layer 5 is made around the light-emitting part (P-type GaAsP layer 5).
In the first example of the conventional opto-semiconductor device shown in FIG. 1, the contact between the P-type GaAsP layer 5 and the Al electrode 8 is positioned at one end of the P-type GaAsP layer 5, so the intensity of light emitted when the device is energized is decreased with the distance from the Al electrode 8 and the light intensity is not uniform throughout the light-emitting area. This is evidenced in the diagram No. 3 (the relationship between the distribution of light output within the light-emitting part and the depth of the PN junction) in the Oki Denki Kenkyu Kaihatsu, (this is shown in figure FIG. 3) showing the light intensity distribution along the longitudinal direction of the P-type GaAsP layer 5.
In the second example of the conventional opto-semiconductor device shown in FIG. 2, the effect of providing the contacting part of the Al electrode at one end of the light-emitting part is eliminated so the uniformity of the light intensity is improved, but as the Al electrode 8 spreads over a wide area, there is a problem of reflection of light at the electrode, and in addition the Al electrode 8 project from the side of the light-emitting part toward adjacent light-emitting part, so it is possible that short-circuiting between the electrodes of adjacent light emitting parts (in an array of light-emitting parts) may occur where the density of the P-type GaAsP layers 5 (light-emitting parts) is increased, i.e., the pitch of the light-emitting parts is reduced.
Furthermore, since both in the first and the second opto-semiconductor devices the Al does not permit passage of light so the light emission from the light-emitting part beneath the electrode is not fully utilized.
Moreover, because a metal is employed for the electrode, crystal cannot be grown on it, and it is difficult to form a three-dimensional device.